1. Field of the Invention
The present invention relates to a method of fabricating a nitride semiconductor light emitting device, and a nitride semiconductor light emitting device fabricated thereby.
2. Description of the Related Art
Nitride semiconductors have been receiving attention as a raw material of blue light emitting diode or blue laser diode.
Such a nitride semiconductor light emitting device is grown on a sapphire substrate or a SiC substrate. Then, a polycrystalline thin film AlyGa1-yN is grown on a sapphire substrate or a SiC substrate at a low temperature as a buffer layer.
Afterward, an n-GaN layer is formed on the buffer layer by growing an undoped GaN layer and a silicon doped n-GaN layer, or a composite structure thereof at a high temperature. Then, a magnesium Mg doped p-GaN layer is formed thereon so as to fabricate a nitride semiconductor light emitting device. A light emitting layer, which is a single quantum well structure or a multi quantum well structure, is formed as a sandwich structure between the n-GaN layer and the p-GaN layer.
The p-GaN layer is formed by doping a GaN layer with Mg atoms in crystal growth. During crystal growth, Mg atoms injected as a doping source are placed at Ga locations to form the p-GaN layer. However, Mg atoms react with hydrogen gas from a carrier gas or a source. As a result, Mg—H complex is formed thereby. Therefore, the Mg—H complex may become a high resistor, for example, about 10 MΩ.
Therefore, a post-activation process is required after forming a p-n junction light emitting device to place the Mg atoms to Ga locations by disjoining Mg—H complex. However, the amount of carrier for light emitting in the activation process is about 2.25×1017/cm3 in the light emitting device. Therefore, it is difficult to form a resistive contact.
Therefore, there are many researches in progress for overcoming the shortcomings arisen by Mg—H complex.